Extending the usable optical bandwidth will increase the generation and strength of nonlinear effects. However, as a solution to increase the capacity of modern optical communication systems using an extended optical bandwidth can still be an attractive option. NLI noise has an approximately logarithmic relationship with the bandwidth of the transmitted signals [1]}. In any logarithmic function, the fastest growing stage is found close to zero, implying that the closest frequency components contribute the most to the generation of nonlinear distortions in a channel of interest, while channels with a large frequency separation present only a small contribution to it. However, ISRS modifies the generation of NLI along the transmission fibres making the answer of how much the throughput can be increased by using a larger optical bandwidth not simple.
